PatchBridge

Bootstrap-resident trampoline. Injected into the bootstrap classloader via Instrumentation.appendToBootstrapClassLoaderSearch. A patched vanilla method carries an inlined INVOKESTATIC PatchBridge.fireEnter(slot, key, self, args) at its head, or PatchBridge.fireExit(slot, key, ...) at every exit (woven by ByteBuddy Advice); slot indexes the Handler the game classloader registered, key is only carried through to it.

One registry serves every phase: slot and key are both minted per INSTALL, so the game side hands the key back as the patch id while the slot stays this class's business.

fireEnter / fireExit observe; fireIntercept / fireModify return a value the advice assigns. All four share one rule: a handler that throws is caught here, and the answer degrades to whatever leaves the patched method untouched.

Re-entrancy is unguarded, deliberately. A handler that reaches the method it patched fires it again until the stack ends — the caller's mistake, and their own stack trace names it. A latch would also drop the nested fires a patch on a recursive method exists to see, and would cost every patch to protect one from itself. The exception is the dispatch path below, which every OTHER patch runs through: weaving that breaks patches its installer never wrote, so Patches refuses it.

Pure JDK only — must never reference any net.minecraft.* / loader class, so that the one copy on the bootstrap loader keeps a single identity across every module layer that patched MC methods live in. NeoForge ModuleClassLoader and Fabric KnotClassLoader both delegate this package to bootstrap.